Process for the preparation of moisture-curable, polyether urethanes with terminal cyclic urea reactive silane groups

ABSTRACT

A process for preparing a moisture-curable, polyether urethane containing terminal cyclic urea/reactive silane groups by reacting at an NCO:OH equivalent ratio of 1.5:1 to 2.5:1 a) a hydroxyl component containing i) a polyether containing two hydroxyl groups and one or more polyether segments, wherein the polyether segments have a number average molecular weight of at least 3000 and a degree of unsaturation of less than 0.04 milliequivalents/g, and ii) a polyether containing one hydroxyl group and one or more polyether segments having a number average molecular weight of 1000 to 15,000, with b) an isocyanate component containing i) a compound containing two isocyanate groups, and ii) a compound containing one isocyanate group, and subsequently reacting this reaction product at an equivalent ratio of isocyanate groups to isocyanate-reactive groups of 0.8:1 to 1.1:1 with c) a compound containing an aspartate group and a reactive silane group to form an intermediate polyether urethane containing terminal non-cyclic urea/reactive silane groups and converting the non-cyclic urea groups to cyclic urea groups by reacting the intermediate polyether urethane.

FIELD OF THE INVENTION

The present invention relates to a process for preparingmoisture-curable polyether urethanes containing terminal cyclicurea/reactive silane groups from polyether polyols having a low degreeof unsaturation and to the use of these polyether urethanes as sealants,adhesives and coatings.

BACKGROUND OF THE INVENTION

Polyether urethanes containing reactive silane groups, also referred toas silane-terminated polyurethanes (STPs), and their use as sealants andadhesives are known and described, e.g., in U.S. Pat. Nos. 5,554,709;4,857,623; 5,227,434 and 6,197,912; and WO 02/06367. Thesilane-terminated polyurethanes may be prepared by various methods. Inone method the silane-terminated polyurethanes are prepared by reactingdiisocyanates with polyether polyols to form isocyanate-terminatedprepolymers, which are then reacted with aminosilanes to form thesilane-terminated polyurethanes. The sealants may also be prepared byreacting unsaturated monools with diisocyanates to form intermediatescontaining unsaturated end groups and then converting these unsaturatedgroups to alkoxysilane groups by hydrosilylation. In another method thesealants are prepared in one step by the reaction of polyether-diolswith isocyanatosilanes

To be useful as sealants the silane-terminated polyurethanes should havea number average molecular weight of 6000 to 20,000. One method ofobtaining this molecular weight is to use polyether diols prepared bythe KOH process and having a molecular weight of 2000 to prepare theisocyanate-terminated prepolymers. The presence of urethane groupscauses the products to have a high viscosity. To achieve suitableapplication viscosities, the high viscosity is reduced by the additionof higher amounts of plasticizer and lesser amounts of fillers,resulting in more expensive sealant products.

Another method of obtaining high molecular weight sealants is by usinghigh molecular weight polyether diols having a low degree ofunsaturation and prepared using special catalysts as described in EP-A0,546,310, EP-A 0,372,561 and DE-A 19,908,562. When these polyetherdiols are used, the resulting sealants have excellent tensile strength,but the sealants are too brittle for many applications because theelongation is too low and the 100% modulus is too high.

The preparation of sealants from mixtures of polyfunctional andmonofunctional silane-terminated polyurethanes is known and disclosed inU.S. Pat. Nos. 5,554,709 and 4,857,623 and WO 02/06367. However, thesereferences do not disclose the use of polyether polyols having a lowdegree of unsaturation and aspartate-functional silanes to prepare thesealants.

The preparation of silane-terminated polyether urethanes fromaspartate-functional silanes is disclosed in U.S. Pat. No. 5,364,955 andWO 98/18843. In both of these references the polyethers used to preparepolyether urethanes do not have a low degree of unsaturation. Inaddition, mixtures of polyfunctional and monofunctionalsilane-terminated polyurethanes are not disclosed. Finally, in thelatter reference the polyethers must contain 15 to 40% by weight ofethylene oxide units.

WO 00/26271 discloses the preparation of silane-terminated polyetherurethanes from polyether polyols having a low degree of unsaturation andaspartate-functional silanes. The products are prepared by reactingdiisocyanates with high molecular weight polyether diols to form NCOprepolymers, which are then capped with aspartate-functional silanes toform silane-terminated polyether urethanes. This application does notdisclose mixtures of disilane-terminated polyether urethanes withpolyether urethanes containing one reactive silane group.

U.S. Pat. No. 6,265,517 describes a similar process for preparingsilane-terminated polyether urethanes from polyether polyols having alow degree of unsaturation and aspartate-functional silanes. The patentrequires the starting polyol to have a monool content of less than 31mole %, and teaches that a relatively high monool content is highlyundesirable because monools react with isocyanates thereby reducingcrosslinking and curing of the prepolymer. The patent also requires theaspartate silanes to be prepared from dialkyl maleates in which thealkyl groups each contain more than four carbon atoms.

EP 0,372,561 discloses polyether urethanes containing reactive silanegroups and prepared from polyether polyols having a low degree ofunsaturation. In addition, polyether urethanes containing one reactivesilane group are disclosed. This application fails to disclose the useof aspartate-functional silanes to incorporate the reactive silanegroups.

The deficiencies of the preceding sealants were overcome in copendingapplications, U.S. Ser. Nos. 10/690,751,10/690,955,10/690,956,10/690,954 and 10/690,931, which describe moisture-curable,alkoxysilane-functional polyether urethanes containing both polyetherurethanes having two or more reactive silane groups and polyetherurethanes having one reactive silane group. The moisture-curablepolyether urethanes are suitable for use as sealants, adhesives andcoatings which possess high tensile strengths and elongations and have areduced 100% modulus when compared with existing products.

In the copending applications the polyether urethane componentcontaining two or more reactive silane groups is prepared from highmolecular weight polyether polyols having a low degree of unsaturation.In addition, at least a portion of the reactive silane groups present inat least one of the two components are incorporated by the use ofsilanes containing secondary amino groups. Finally, the polyetherurethane components described in the copending applications are preparedseparately and subsequently blended to form the moisture-curablepolyether urethanes according to the invention.

Copending application, U.S. Ser. No. 10/690,953 describes a process forsimultaneously preparing moisture-curable polyether urethanes containinga mixture of polyether urethane component having two or more reactivesilane groups and a polyether urethane component having one reactivesilane group instead of being prepared separately and mixed. The mixtureof polyether urethanes retains all of the valuable properties of thepolyether urethanes disclosed in the previously described copendingapplications.

A disadvantage of the moisture-curable polyether urethanes described inthe preceding copending applications is that they are not storage stableat moderately elevated temperatures of 50 to 90° C., which may bepresent in a drum stored in a hot climate.

Accordingly, it is an object of the present invention to provide aprocess for preparing moisture-curable polyether urethanes at lowerproduction viscosities, in which the resulting products are storagestable at elevated temperatures and also retain all of the valuableproperties of the polyether urethanes disclosed in the precedingcopending applications, i.e., the products are suitable for use assealants, adhesives and coatings which possess high tensile strengthsand elongations and have a reduced 100% modulus.

This object may be achieved with the process of the present invention inwhich the moisture-curable polyether urethanes containing a mixture ofpolyether urethane component having two or more reactive silane groupsand a polyether urethane component having one reactive silane group areprepared simultaneously and in which the polyether urethanes containterminal cyclic urea/reactive silane groups.

The present invention is based on the surprising discovery that thenon-cyclic urea groups formed by the reaction of isocyanate groups andaspartate silane groups decompose back into the starting components whenstored at moderately elevated temperatures. In accordance with thepresent invention this decomposition is prevented by converting thenon-cyclic urea groups into cyclic urea groups, which are thermallystable.

It is surprising that the polyether urethanes obtained according to theprocess of present invention can be used to prepare cured resins thatpossess the same properties as those obtained in accordance with thecopending applications because the presence of cyclic urea groups wouldbe expected to result in less flexible cured resins that would not havethe same elongation and 100% modulus as cured resins prepared frompolyether urethanes containing non-cyclic urea groups.

SUMMARY OF THE INVENTION

The present invention relates to a process for preparing amoisture-curable, polyether urethane containing terminal cyclicurea/reactive silane groups by reacting at an NCO:OH equivalent ratio of1.5:1 to 2.5:1

-   a) a hydroxyl component containing    -   i) 20 to 100% by weight, based on the weight of component a), of        a polyether containing two hydroxyl groups and one or more        polyether segments, wherein the polyether segments have a number        average molecular weight of at least 3000 and a degree of        unsaturation of less than 0.04 milliequivalents/g, provided that        the sum of the number average molecular weights of all of the        polyether segments per molecule averages 6000 to 20,000, and    -   ii) 0 to 80% by weight, based on the weight of component a), of        a polyether containing one hydroxyl group and one or more        polyether segments having a number average molecular weight of        1000 to 15,000, with-   b) an isocyanate component containing    -   i) 20 to 100% by weight, based on the weight of component b), of        a compound containing two isocyanate groups, and    -   ii) 0 to 80% by weight, based on the weight of component b), of        a compound containing one isocyanate group,        provided that total percentages of a-ii) and b-ii) add up to at        least 10, to form an isocyanate-containing reaction product and        subsequently reacting this reaction product at an equivalent        ratio of isocyanate groups to isocyanate-reactive groups of        0.8:1 to 1.1:1 with-   c) a compound containing an isocyanate-reactive group and one    reactive silane groups in which at least 10 mole % of component c)    is a compound corresponding to the formula    -   wherein    -   X represents identical or different organic groups which are        inert to isocyanate groups below 100° C., provided that at least        two of these groups are alkoxy or acyloxy groups,    -   Y represents a linear or branched alkylene group containing 1 to        8 carbon atoms,    -   R₁ and R₂ are identical or different and represent organic        groups which are inert to isocyanate groups at a temperature of        100° C. or less and    -   R₃ and R₄ are identical or different and represent hydrogen or        organic groups which are inert towards isocyanate groups at a        temperature of 100° C. or less, to form an intermediate        polyether urethane containing at least a portion of terminal        non-cyclic urea/reactive silane groups corresponding to formula        II        and converting the non-cyclic urea groups to cyclic urea groups        by reacting the intermediate polyether urethane in the presence        of an acid catalyst and heat to form terminal cyclic        urea/reactive silane groups corresponding to formula III and/or        formula IV

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention the term “reactive silanegroup” means a silane group containing at least two alkoxy or acyloxygroups as defined by substituent “X”. A silane group containing two orthree alkoxy and/or acyloxy groups is considered to be one reactivesilane group. Also, a urethane is a compound containing one or moreurethane and/or urea groups. These compounds preferably contain one ormore urethane groups and may optionally contain urea groups. Morepreferably, these compounds contain both urethane and urea groups. Theisocyanate-containing reaction products used for preparing themoisture-curable polyether urethanes may be prepared by several methods.For example, they may be prepared by reacting a mixture of polyetherdiol a-i) and polyether monool a-ii) with an excess of diisocyanateb-i), to form an isocyanate-containing reaction product containing NCOprepolymers and monoisocyanates formed by the reaction of one mole of adiisocyanate with one mole of a polyether monool. In this embodimentpolyether monool a-ii) is present in an amount of at least 10% byweight, based on the weight of component a).

In another embodiment the isocyanate-containing reaction products areprepared by reacting polyether diol a-i) with an excess of diisocyanateb-i) and monoisocyanate b-ii) to form an isocyanate-containing reactionproduct containing NCO prepolymers and monoisocyanates formed by thereaction of one mole of a monoisocyanate and one mole of a diisocyanatewith one mole of a polyether diol. In this embodiment monoisocyanateb-ii) is present in an amount of at least 10% by weight, based on theweight of component b).

It is also possible to use a combination of the preceding processes inwhich both polyether monools a-ii) and monoisocyanates b-ii) arepresent.

The isocyanate-containing reaction products are prepared by reacting theisocyanate component with the polyether component at an NCO:OHequivalent ratio of a 1.5:1 to 2.5:1, preferably 1.8:1 to 2.2:1 and morepreferably 1.9:1 to 2.1:1 and most preferably 2:1. It is especiallypreferred to react one mole of the isocyanate component for eachequivalent of hydroxyl groups.

When preparing the isocyanate-containing reaction product fromdiisocyanate b-i), polyether diol a-i) and polyether monool a-ii) at anNCO:OH equivalent ratio of 2:1, the reaction mixture contains the 2/1adduct of the diisocyanate and diol; minor amounts of higher molecularweight oligomers, such as the 3/2 adduct; a monoisocyanate, which is the1/1 adduct of the monool and diisocyanate; non-functional polymers,which are formed by the reaction of two molecules of the monool with onemolecule of the diisocyanate; various products containing both diols andmonools; and a minor amount of unreacted diisocyanate, which can beremoved, e.g., by distillation, or which can remain in the reactionmixture.

To form the moisture-curable polyether urethanes according to theinvention the isocyanate-containing reaction products are reacted withcompounds c) containing reactive silane groups at equivalent ratio ofisocyanate groups to isocyanate-reactive groups of 0.8:1 to 1.1:1,preferably 0.9:1 to 1.05:1 and more preferably about 1:1.

The moisture-curable polyether urethanes may also be prepared byreacting an excess of diisocyanates b) with aminosilanes c) to form amonoisocyanate and then reacting the resulting monoisocyanate with amixture of polyethers a-i) and a-ii) to form the polyether urethanes.

The moisture-curable, polyether urethanes obtained according to theprocess of the present invention contain polyether urethanes A), whichcontain two or more, preferably two, reactive silane groups, andpolyether urethanes B), which contain one reactive silane group. Alsopresent are polymers C), which are the reaction products of unreactedisocyanates b) with aminosilanes c). Polymers C) are preferably presentin an amount of less then 5% by weight.

The reaction mixture also contains non-functional polymers D), which areformed by the reaction of two molecules of the monool with one moleculeof the diisocyanate, two molecules of the monoisocyanate with onemolecule of the diol, or one molecule of the monool with one molecule ofa monoisocyanate. Non-functional polymers D) are generally present in anamount of less than 30% by weight.

In accordance with the present invention it is also possible to adjustthe NCO:OH equivalent ratio to form additional amounts of non-functionalpolymers D) are formed from the reactants as previously described. Thesepolymers remain in the reaction mixture and function as plasticizersduring the subsequent use of the moisture-curable, polyether urethanesaccording to the invention.

Suitable polyethers for use as component a-i) include polyoxypropylenepolyethers containing two hydroxyl groups and optionally up to 20% byweight, based on the weight of component a-i), of polyethers containingmore than 2 hydroxyl groups. The polyethers contain one or more,preferably one, polyether segment having a number average molecularweight of 3000 to 20,000, preferably 6000 to 15,000 and more preferably8000 to 12,000. When the polyether segments have a number averagemolecular weight of 3000, for example, then two or more of thesesegments must be present so that the number average molecular weights ofall of the polyether segments per molecule averages 6000 to 20,000.

Suitable polyols for preparing polymers a) are polyether polyols, insome cases polyoxypropylene polyols, in many instances diols, having anumber average molecular weight of 3000 to 20,000, preferably 6000 to15,000, and more preferably 8000 to 12,000. The polyethers can have amaximum total degree of unsaturation of less than 0.04milliequivalents/g, in some cases less than 0.02 meqlg (meq/g), in othercases less than 0.01 meq/g and in some situations 0.007 meq/g or less.The amount of unsaturation will vary depending on the method used toprepare the polyether as well as the molecular weight of the polyerther.Such polyether diols are known and can be produced, as a non-limitingexample, by the propoxylation of suitable starter molecules. As anothernon-limiting example, minor amounts (up to 20% by weight, based on theweight of the polyol) of ethylene oxide can be used. If ethylene oxideis used, it can be used as the initiator for or to cap the polypropyleneoxide groups. Non-limiting examples of suitable starter moleculesinclude diols such as ethylene glycol, propylene glycol, 1,3-butanediol,1,4-butanediol, 1,6 hexanediol and 2-ethylhexanediol-1,3. Also suitableare polyethylene glycols and polypropylene glycols.

Suitable methods for preparing polyether polyols are known and aredescribed, for example, in EP-A 283 148, U.S. Pat. No. 3,278,457, U.S.Pat. No. 3,427,256, U.S. Pat. No. 3,829,505, U.S. Pat. No. 4,472,560.U.S. Pat. No. 3,278,458, U.S. Pat. No. 3,427,334, U.S. Pat. No.3,941,849, U.S. Pat. No. 4,721,818, U.S. Pat. No. 3,278,459, U.S. Pat.No. 3,427,335 and U.S. Pat. No. 4,355,188. They are preferably preparedusing double metal cyanides as catalysts.

In addition to the polyether polyols, minor amounts (up to 20% byweight, based on the weight of the polyol) of low molecular weightdihydric and trihydric alcohols having a molecular weight 32 to 500 canalso be used. Suitable examples include ethylene glycol, 1,3-butandiol,1,4-butandiol, 1,6-hexandiol, glycerine or trimethylolpropane. However,the use of low molecular weight alcohols is less preferred.

Polyethers a-i) are present in a amount of 20 to 100% by weight. Whenpolyether monools a-ii) are used as the sole monofunctional component,polyethers a-i) are present in a minimum amount of 20% by weight,preferably 30% by weight and more preferably 40% by weight, and amaximum amount of 100% by weight, preferably 90% by weight, morepreferably 80% by weight and most preferably 70% by weight. Thepreceding percentages are based on the total weight of polyethers a).

Suitable polyether monools a-ii) are polyether monools having a numberaverage molecular weight of 1000 to 15,000, preferably 3000 to 12,000and more preferably 6000 to 12,000. The polyether monools are preparedby the alkoxylation of monofunctional starting compounds with alkyleneoxides, preferably ethylene oxide, propylene oxide or butylene oxide,more preferably propylene oxide. If ethylene oxide is used, it is usedin an amount of up to 40% by weight, based on the weight of thepolyether. The polyethers are preferably prepared either by the KOHprocess or by mixed metal cyanide catalysis. The latter process resultsin products with low a degree of unsaturation.

In many cases, the polyethers, which as a non-limiting example can bepolypropylene oxide polyethers have a maximum total degree ofunsaturation of less than 0.04 milliequivalents/g (meq/g) in some casesless than 0.02 meqlg, in other cases less than 0.01 meq/g and in somesituations 0.007 meq/g or less. The amount of unsaturation will varydepending on the method used to prepare the polyether as well as themolecular weight of the polyerther. Such polyether monools are known andcan be produced, as a non-limiting example by the methods set forthpreviously for preparing polyethers, a non-limiting example being thepolyoxypropylene polyols by the propoxylation of suitable startermolecules. In another non-limiting example, minor amounts (up to 20% byweight, based on the weight of the polyol) of ethylene oxide can also beused. As with the polyethers a-i), if ethylene oxide is used, it can beused as the initiator for or to cap the polypropylene oxide groups.

Examples of suitable starter molecules include aliphatic, cycloaliphaticand araliphatic alcohols, phenol and substituted phenols, such asmethanol, ethanol, the isomeric propanols, butanols, pentanols andhexanols, cyclohexanol and higher molecular weight compounds such asnonylphenol, 2-ethylhexanol and a mixture of C₁₂ to C₁₅, linear, primaryalcohols (Neodol 25, available from Shell). Also suitable areunsaturated alcohols such as allyl alcohol; and hydroxy functionalesters such as hydroxyethyl acetate and hydroxyethyl acrylate. Preferredare the higher molecular weight monohydroxy compounds, especially nonylphenol and mixtures of C₁₂ to C₁₅, linear, primary alcohols.

When polyethers a-ii) are present as the sole monofunctional component,they are present in a minimum amount of 0% by weight, preferably 10% byweight, more preferably 20% by weight and most preferably 30% by weight,and a maximum amount of 80% by weight, preferably 70% by weight and morepreferably 60% by weight. The preceding percentages are based on thetotal weight polyethers a).

Suitable isocyanates b-i) include the known monomeric organicdiisocyanates represented by the formula, R(NCO)₂, in which R representsan organic group obtained by removing the isocyanate groups from anorganic diisocyanate having a molecular weight of 112 to 1,000,preferably 140 to 400. Preferred diisocyanates are those represented bythe above formula in which R represents a divalent aliphatic hydrocarbongroup having from 4 to 18 carbon atoms, a divalent cycloaliphatichydrocarbon group having from 5 to 15 carbon atoms, a divalentaraliphatic hydrocarbon group having from 7 to 15 carbon atoms or adivalent aromatic hydrocarbon group having 6 to 15 carbon atoms.

Examples of suitable organic diisocyanates include 1,4-tetramethylenediisocyanate, 1,6-hexamethylene diisocyanate,2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylenediisocyanate, cyclohexane-1,3- and -1,4-diisocyanate,1-isocyanato-2-isocyanatomethyl cyclopentane,1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophoronediisocyanate or IPDI), bis-(4-isocyanato-cyclohexyl)-methane, 1,3- and1,4-bis-(isocyanatomethyl)-cyclohexane,bis-(4-isocyanatocyclo-hexyl)-methane, 2,4′-diisocyanato-dicyclohexylmethane, bis-(4-isocyanato-3-methyl-cyclohexyl)-methane,α,α,α′,α′-tetra-methyl-1,3- and/or -1,4-xylylene diisocyanate,1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4- and/or2,6-hexahydro-toluylene diisocyanate, 1,3- and/or 1,4-phenylenediisocyanate, 2,4- and/or 2,6-toluylene diisocyanate, 2,4- and/or4,4′-diphenylmethane diisocyanate and 1,5-diisocyanato naphthalene andmixtures thereof.

Monomeric polyisocyanates containing 3 or more isocyanate groups such as4-isocyanatomethyl-1,8-octamethylene diisocyanate and aromaticpolyisocyanates such as 4,4′,4″-triphenylmethane triisocyanate andpolyphenyl polymethylene polyisocyanates obtained by phosgenatinganiline/formaldehyde condensates may also be used in an amount of up to20% by weight, based on the weight of isocyanates b). Also suitable,although less preferred, are polyisocyanate adducts prepared from thepreceding monomeric polyisocyanates and containing isocyanurate,uretdione, biuret, urethane, allophanate, iminooxadiazine dione,carbodiimide and/or oxadiazinetrione groups.

Preferred diisocyanates include bis-(4-isocyanatocyclohexyl)-methane,1,6-hexamethylene diisocyanate, isophorone diisocyanate,α,α,α′,α′-tetramethyl-1,3- and/or -1,4-xylylene diisocyanate, 2,4-and/or 2,6-toluylene diisocyanate, and 2,4- and/or 4,4′-diphenylmethanediisocyanate. Especially preferred are isophorone diisocyanate,2,4-toluylene diisocyanate and mixtures of 2,4- and 2,6-toluylenediisocyanate.

Diisocyanates b-i) are present in a amount of up to 100% by weight. Whenmonoisocyanates b-ii) are used as the sole monofunctional component,diisocyanates b-i) are present in a minimum amount of 20% by weight,preferably 30% by weight and more preferably 40% by weight, and amaximum amount of 100% by weight, preferably 90% by weight, morepreferably 80% by weight and most preferably 70% by weight. Thepreceding percentages are based on the total weight of isocyanates b).

Suitable isocyanates b-ii) include those corresponding to the formulaR(NCO), wherein R is defined as previously set forth with regard to theorganic diisocyanates. Suitable monoisocyanates include thosecorresponding to the diisocyanates previously set forth. Examplesinclude butyl isocyanate, hexyl isocyanate, octyl isocyanate,2-ethylhexyl isocyanate, stearyl isocyanate, cyclohexyl isocyanate,phenyl isocyanate and benzyl isocyanate.

When monoisocyanates b-ii) are present as the sole monofunctionalcomponent, they are present in a minimum amount of 0% by weight,preferably 10% by weight, more preferably 20% by weight and mostpreferably 30% by weight, and a maximum amount of 80% by weight,preferably 70% by weight and more preferably 60% by weight. Thepreceding percentages are based on the total weight isocyanates b).

Suitable compounds c) containing reactive silane groups are thosecorresponding to formula I

wherein

-   X represents identical or different organic groups which are inert    to isocyanate groups below 100° C., provided that at least two of    these groups are alkoxy or acyloxy groups, preferably alkyl or    alkoxy groups having 1 to 4 carbon atoms and more preferably alkoxy    groups,-   Y represents a linear or branched alkylene group containing 1 to 8    carbon atoms, preferably a linear group containing 2 to 4 carbon    atoms or a branched group containing 5 to 6 carbon atoms, more    preferably a linear group containing 3 carbon atoms,-   R₁ and R₂ are identical or different and represent organic groups    which are inert to isocyanate groups at a temperature of 100° C. or    less, preferably alkyl groups having 1 to 9 carbon atoms, more    preferably alkyl groups having 1 to 4 carbon atoms, such as methyl,    ethyl or butyl groups and-   R₃ and R₄ are identical or different and represent hydrogen or    organic groups which are inert towards isocyanate groups at a    temperature of 100° C. or less, preferably hydrogen.

Especially preferred are compounds in which X represents methoxy, ethoxygroups or propoxy groups, more preferably methoxy or ethoxy groups, andY is a linear group containing 3 carbon atoms.

The compounds of formula I are prepared by reacting aminosilanescorresponding to formula VH₂N—Y—Si—(X)₃  (V)with maleic or fumaric acid esters corresponding to formula VIR₁OOC—CR₃═CR₄—COOR₂  (VI)

Examples of suitable aminoalkyl alkoxysilanes and aminoalkylacyloxysilanes corresponding to formula V include3-aminopropyl-triacyloxysilane, 3-aminopropyl-methyldimethoxysilane;6-aminohexyl-tributoxysilane; 3-aminopropyl-trimethoxysilane;3-aminopropyl-triethoxysilane; 3-aminopropyl-methyldiethoxysilane;5-aminopentyl-trimethoxysi lane; 5-aminopentyl-triethoxysilane;4-amino-3,3-dimethyl-butyl-trimethoxysilane; and3-aminopropyl-triisopropoxysilane. 3-amino-propyl-trimethoxysilane and3-aminopropyl-triethoxysilane are particularly preferred.

Examples of optionally substituted maleic or fumaric acid esterssuitable for preparing the aspartate silanes include the dimethyl,diethyl, dibutyl (e.g., di-n-butyl), diamyl, di-2-ethylhexyl esters andmixed esters based on mixture of these and/or other alkyl groups ofmaleic acid and fumaric acid; and the corresponding maleic and fumaricacid esters substituted by methyl in the 2- and/or 3-position. Thedimethyl, diethyl and dibutyl esters of maleic acid are preferred, whilethe diethyl esters are especially preferred.

The reaction of primary amines with maleic or fumaric acid esters toform the aspartate silanes of formula III is known and described, e.g.,in U.S. Pat. No. 5,364,955, which is herein incorporated by reference.

The compounds corresponding to formula I are preferably used ascomponent c). To obtain the benefits of the present invention, theyshould be present in an amount of at least 10% by weight, preferably atleast 30% by weight, more preferably at least 50% by weight and mostpreferably at least 80% by weight. In addition to the compounds offormula I, which are required according to the present invention,component c) may also contain aminosilanes that do not correspond toformula I, such as those corresponding to the formula

wherein

-   X and Y are as previously defined and-   R₅ represents hydrogen or an organic group which is inert to    isocyanate groups at a temperature of 100° C. or less, provided that    R₅ is not a succinate group, preferably hydrogen or an alkyl,    cycloalkyl or aromatic group having 1 to 12 carbon atoms and more    preferably an alkyl, cycloalkyl or aromatic group having 1 to 8    carbon atoms, or R₅ represents a group corresponding to formula VIII    —Y—Si—(X)₃  (VIII)

Examples of suitable aminoalkyl alkoxysilanes and aminoalkylacyloxysilanes of formula VII, which contain primary amino groups, arethe compounds of formula V that have previously been described assuitable for preparing the aspartate silanes of formula I.

Examples of suitable aminoalkyl alkoxysilanes and aminoalkylacyloxysilanes of formula VII, which contain secondary amino groups,include N-phenylaminopropyl-trimethoxysilane (available as A-9669 fromOSI Corporation), bis-(γ-trimethoxysilylpropyl)amine (available asA-1170 from OSI Corporation), N-cyclohexylaminopropyl-4-riethoxysilane,N-methylaminopropyl-trimethoxysilane,N-butylaminopropyl-trimethoxy-silane,N-butylaminopropyl-triacyloxysilane,3-(N-ethyl)amino-2-methyl-propyl-trimethoxysilane,4-(N-ethyl)amino-3,3-dimethylbutyl-trimethoxysilane and thecorresponding alkyl diethoxy, alkyl dimethoxy and alkyldiacyloxysilanes, such as3-(N-ethyl)amino-2-methylpropyl-methyl-dimethoxysilane.

The conversion of the non-cyclic urea groups into cyclic urea groupstakes place according the following reaction

The reaction is carried out in the presence of a catalyst and heat.Suitable-catalysts are Brønsted acids, such as mineral acids, carboxylicacids, sulfonic acids and phenols. Preferred catalysts are carboxylicacids, such as formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, malonic acid, phthalic acid, and 1,2,3-tricarboxylicpropane. Especially preferred are acetic acid and 2-ethyl hexanoic acid.

Higher temperatures accelerate the conversion of the non-cyclic ureagroups into cyclic urea groups. Suitable reaction temperatures are from50 to 200° C. Very low temperatures require long reaction times andresult in a very yellow product. Very high temperatures require onlyshort reaction times, but also result in yellow products. The preferredrange for minimizing the development of the yellow color is from 70 to130° C., more preferably from 90 to 120° C. and most preferably from 100to 120° C.

The conversion of non-cyclic urea groups into cyclic urea groups isaccompanied by the release of a mole of alcohol from the succinyl ester.The generated alcohol and the catalyst can be removed from the reactionmixture, for example, by vacuum distillation, or they can be left in theproduct. If left in the product the released alcohols may undergo atransetherication reaction with the alkoxy groups on the silane. Whetherthe released alcohols are removed or not is of no consequence, since theproducts formed with or without vacuum purification, when formulatedinto a sealant or adhesive, undergo moisture cure to give curedcompositions of equivalent performance.

The transetherification reaction can be used to alter the reactivity ofthe polyether urethanes according to the invention. For example, if amethoxysilane group is converted to an ethoxysilane group or abutoxysilane group, the reactivity of the resulting alkoxysilane groupswill be substantially reduced. To the contrary if an ethoxysilane groupor a butoxysilane group is converted to a methoxysilane group, thereactivity of the resulting alkoxysilane groups will be substantiallyincreased.

The compositions obtained by the process of the present invention may becured in the presence of water or moisture to prepare coatings,adhesives or sealants. The compositions cure by “silanepolycondensation” from the hydrolysis of alkoxysilane groups to formSi—OH groups and their subsequent reaction with either Si—OH or Si—ORgroups to form siloxane groups (Si—O—Si).

Suitable acidic or basis catalysts may be used to promote the curingreaction. Examples include acids such as para-toluene sulfonic acid;metallic salts such as dibutyl tin dilaurate; tertiary amines such astriethylamine or triethylene diamine; and mixtures of these catalysts.The previously disclosed, low molecular weight, basic aminoalkyltrialkoxysilanes, also accelerate hardening of the compounds accordingto the invention.

The one-component compositions generally may be either solvent-free orcontain up to 70%, preferably up to 60% organic solvents, based on theweight of the one-component composition, depending upon the particularapplication. Suitable organic solvents include those which are knownfrom either from polyurethane chemistry or from coatings chemistry.

The compositions may also contain known additives, such as levelingagents, wetting agents, flow control agents, antiskinning agents,antifoaming agents, fillers (such as chalk, lime, flour, precipitatedand/or pyrogenic silica, aluminum silicates and high-boiling waxes),viscosity regulators, plasticizers, pigments, dyes, UV absorbers andstabilizers against thermal and oxidative degradation.

The one-component compositions may be used with any desired substrates,such as wood, plastics, leather, paper, textiles, glass, ceramics,plaster, masonry, metals and concrete. They may be applied by standardmethods, such as spraying, spreading, flooding, casting, dipping,rolling and extrusion.

The one-component compositions may be cured at ambient temperature or atelevated temperatures. Preferably, the moisture-curable compositions arecured at ambient temperatures.

The invention is further illustrated but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

EXAMPLES

Preparation of Silane Functional Aspartate 1

An aspartate resin was prepared according to U.S. Pat. No. 4,364,955. Toa 5 liter flask fitted with agitator, thermocouple, nitrogen inlet andaddition funnel with condenser were added 1483 g (8.27 equivalents) of3-amino-propyl-trimethoxysilane (Silquest A-1110, available from OSICorporation). The addition funnel was used to admit 1423.2 g (8.27equivalents) of diethyl maleate over a two hour period. The temperatureof the reactor was maintained at 25° C. during the addition. The reactorwas maintained at 25° C. for an additional five hours at which time theproduct was poured into glass containers and sealed under a blanket ofnitrogen. After one week the unsaturation number was 0.6 indicating thereaction was ˜99% complete.

Polyether Diol 1

A polyoxypropylene diol (Acclaim 12200, unsaturation=0.007 meq/gavailable from Bayer Corporation) having a functionality of 2 and anequivalent weight of 5783.

Polyether Monool 2

203 g (1.00 eq) of Neodol 25 monool (available from Shell Chemical) werecharged to a stainless-steel reactor. Zinc hexacyanocobaltate-tert-butylalcohol complex (0.143 g, prepared as described in U.S. Pat. No.5,482,908) was added and the mixture was heated with stirring undervacuum at 130° C. for one hour to remove traces of water from the monoolstarter. Propylene oxide (8547 g, 194.2 eq) was introduced into thereactor over 6 hours. After the epoxide addition was completed, themixture was heated to 130° C. until no further pressure decreaseoccurred. The product was vacuum stripped and then drained from thereactor. The resulting polyether had an OH number of 6.4, an equivalentweight of 8750, a functionality of 1, and an unsaturation of less than0.01 meq/g.

Example 1 Preparation of Cyclic Urea/Reactive Silane TerminatedPolyurethane (STP) 1 in situ from a 74:26 diol:monool Mixture

A 5 liter round bottom flask was fitted with agitator, nitrogen inlet,condenser, heater and addition funnel. Into the flask were charged 127.9g (1.15 eq) of isophorone diisocyanate, 2691.6 g (0.47 eq) of polyetherdiol 1, 946.7 g (0.11 eq) of polyether monool 2 and 0.78 g of dibutyltindilaurate. The reaction was heated to 60° C. for 8 hours until the NCOcontent was 0.58% (theoretical=0.63%). 202.2 g (0.55 eq) of silanefunctional aspartate 1 were added and the flask was heated at 60° C. foran additional 1 hour until no NCO remained as determined by an IRspectrum. 19.9 g of glacial acetic acid were added and the temperaturewas raised to 110° C. The reaction mixture was held at 110° C. for threehours until an IR spectrum showed the urea peak had disappeared and acyclic urea peak had appeared. 19.8 g of vinyl trimethoxysilane wereadded as moisture scavenger; and 9.9 g of butylated hydroxy toluene and6.1 g of Naugard 445 (available from Crompton) were added asantioxidants. The resulting product had a viscosity of 54,000 mPa·s at25° C.

Comparative Example 2 Preparation of Non-Cyclic Urea/Reactive SilaneTerminated Polyurethane (STP) 2 in situ from a 74:26 diol:monool Mixture

A 3 liter round bottom flask was fitted with agitator, nitrogen inlet,condenser, heater and addition funnel. Into the flask were charged 80.0g (0.72 eq) of isophorone diisocyanate, 1680.4 g (0.31 eq) of polyetherdiol 1, 591.7 g (0.07 eq) of polyether monool 2 and 0.53 g of dibutyltindilaurate. The reaction was heated to 60° C. for 8 hours until the NCOcontent was 0.60% (theoretical=0.62%). 126.4 g (0.34 eq) of silanefunctional aspartate 1 were added and the flask was heated at 60° C. foran additional 1 hour until no NCO remained as determined by an IRspectrum. 5.5 g of vinyl trimethoxysilane were added as moisturescavenger; and 6.2 g of butylated hydroxy toluene and 3.7 g of Naugard445 (available from Crompton) were added as antioxidants. The resultingproduct had a viscosity of 34,700 mPa·s at 25° C.

Heat Aging of Silanes

Into unlined steel cans were placed 300 g of silane. Four cans of eachresin were placed into a 90° C. oven. One can of each resin was removedeach week and the viscosities were determined. The following table setsforth the change in viscosity over the testing period. Viscosityprofile, cps @ 90° C. Resin Initial 1 week 2 weeks 3 weeks 4 weeks STP 1421 454 505 449 551 STP 2 (Comparison) 541 448 210 — 194Formulation of Silane Sealants

The STP's prepared in situ were formulated into sealants using thefollowing typical formulation and procedure.

Procedure

The following is the standard sealant formulation and procedure used toformulate all of the STP's for testing. Values given for each formulacomponent are percent by weight of the total formula weight. Ahigh-speed centrifugal mixer was used to mix the formulation componentsin the steps given below. Each mixing period was one minute in length ata speed of 2200 rpm.

Step 1:

To a clean dry mixing container were charged the following: STP 37.5Plasticizer 17.5 Adhesion Promoter 0.8 Catalyst 0.1 Desiccant 0.5

The ingredients were mixed for one minute in length at a speed of 2200rpm.

Step 2:

A portion of the filler was added to the mixing container. Filler 23.6

The ingredients were mixed for one minute at a speed of 2200 rpm.

Step 3:

The remaining filler was added to the mixing container. Filler 20.0

The ingredients were mixed for one minute in length at a speed of 2200rpm.

Step 4:

The side of the mix container was scraped and the ingredients were mixedfor one additional minute at a speed of 2200 rpm to incorporate all ofthe filler into the mixture.

Step 5:

The resulting product was degassed at 50° C. and under full vacuum (>28mm Hg) for one hour. The material was used immediately. Exxon JayflexDIDP was used as the plasticizer. An aminosilane (Silquest A-1120,available from OSI Corporation) was used as the adhesion promoter. Avinyltrimethoxysilane (Silquest A-171, available from OSI Corporation)was used as the desiccant. The filler used was Specialty Minerals UltraP Flex precipitated calcium carbonate (mean particle size of 0.07microns). The catalyst used was dibutyltin dilaurate.

Cure and Testing of Silane Sealants

The sealant formulations were cast onto 0.25 inch thick polyethylenesheets and cured at standard conditions of 20° C., 50% relative humidityfor at least two weeks before testing. Tensile strength, percentelongation and 100% modulus were determined according to ASTM D-412. Die“C” tear strengths were determined according to ASTM D-624. The resultsare set forth in the following table.

Examples 3-12 Tensile Properties for Sealants Prepared from STP 1 andComparative STP 2

Percent Tensile 100% Tear Exam- Elongation Strength Modulus Strength ple(%) (psi) (psi) (pli) Cyclic Urea STP 1 3 Initial (No Heat) 244 309 17931 4 1 Wk @ 70 C. 259 356 187 31 5 1 Wk @ 90 C. 256 319 178 32 6 4 Wks @70 C. 265 342 177 34 7 4 Wks @ 90 C. 288 312 171 32 Urea STP 2 8 Initial(No Heat) 379 311 144 28 9 1 Wk @ 70 C. 221 78 46 7 10 1 Wk @ 90 C. 1010 10 5 11 4 Wks @ 70 C. 98 44 39 11 12 4 Wks @ 90 C. 10 10 10 5

The sealant properties of the preceding examples demonstrate that thepolyether urethanes containing terminal cyclic urea/reactive silanegroups and prepared by the in situ process according to the inventionare more heat stable than the comparitive polyether urethanes containingterminal non-cyclic urea/reactive silane groups and prepared by the insitu process.

Although the invention had been described in detail in the foregoing forthe purpose of illustration, it was to be understood that such detailwas solely for that purpose and that variations can be made therein bythose skilled in the art without departing from the spirit and scope ofthe invention except as it may be limited by the claims.

1. A process for preparing a moisture-curable, polyether urethanecontaining terminal cyclic urea/reactive silane groups which comprisesreacting at an NCO:OH equivalent ratio of 1.5:1 to 2.5:1 a) a hydroxylcomponent containing i) 20 to 100% by weight, based on the weight ofcomponent a), of a polyether containing two hydroxyl groups and one ormore polyether segments, wherein the polyether segments have a numberaverage molecular weight of at least 3000 and a degree of unsaturationof less than 0.04 milliequivalents/g, provided that the sum of thenumber average molecular weights of all of the polyether segments permolecule averages 6000 to 20,000, and ii) 0 to 80% by weight, based onthe weight of component a), of a polyether containing one hydroxyl groupand one or more polyether segments having a number average molecularweight of 1000 to 15,000, with b) an isocyanate component containing i)20 to 100% by weight, based on the weight of component b), of a compoundcontaining two isocyanate groups, and ii) 0 to 80% by weight, based onthe weight of component b), of a compound containing one isocyanategroup, provided that total percentages of a-ii) and b-ii) add up to atleast 10, to form an isocyanate-containing reaction product andsubsequently reacting this reaction product at an equivalent ratio ofisocyanate groups to isocyanate-reactive groups of 0.8:1 to 1.1:1 withc) a compound containing an isocyanate-reactive group and one reactivesilane groups in which at least 10 mole % of component c) is a compoundcorresponding to the formula

wherein X represents identical or different organic groups which areinert to isocyanate groups below 100° C., provided that at least two ofthese groups are alkoxy or acyloxy groups, Y represents a linear orbranched alkylene group containing 1 to 8 carbon atoms, R₁ and R₂ areidentical or different and represent organic groups which are inert toisocyanate groups at a temperature of 100° C. or less and R₃ and R₄ areidentical or different and represent hydrogen or organic groups whichare inert towards isocyanate groups at a temperature of 100° C. or less,to form an intermediate polyether urethane containing at least a portionof terminal non-cyclic urea/reactive silane groups corresponding toformula II

and converting the non-cyclic urea groups to cyclic urea groups byreacting the intermediate polyether urethane in the presence of an acidcatalyst and heat to form terminal cyclic urea/reactive silane groupscorresponding to formula III and/or formula IV


2. The process of claim 1 wherein at least 50 mole % of component c) isa compound corresponding to formula I.
 3. The process of claim 1 whereinat least 80 mole % of component c) is a compound corresponding toformula I and X represents identical or different alkoxy groups having 1to 4 carbon atoms, Y represents a linear radical containing 2 to 4carbon atoms or a branched radical containing 5 to 6 carbon atoms and R₁and R₂ are identical or different and represent alkyl groups having 1 to4 carbon atoms and R₃ and R₄ represent hydrogen.
 4. The process of claim1 wherein component a-i) is present in an amount of 20 to 90% by weight,based on the weight of component a); and component a-ii) is present inan amount of 10 to 80% by weight, based on the weight of component a).5. The process of claim 2 wherein component a-i) is present in an amountof 20 to 90% by weight, based on the weight of component a); andcomponent a-ii) is present in an amount of 10 to 80% by weight, based onthe weight of component a).
 6. The process of claim 3 wherein componenta-i) is present in an amount of 20 to 90% by weight, based on the weightof component a); and component a-ii) is present in an amount of 10 to80% by weight, based on the weight of component a).
 7. The process ofclaim 1 wherein component b-i) is present in an amount of 20 to 90% byweight, based on the weight of component b); and component b-ii) ispresent in an amount of 10 to 80% by weight, based on the weight ofcomponent b).
 8. The process of claim 2 wherein component b-i) ispresent in an amount of 20 to 90% by weight, based on the weight ofcomponent b); and component b-ii) is present in an amount of 10 to 80%by weight, based on the weight of component b).
 9. The process of claim3 wherein component b-i) is present in an amount of 20 to 90% by weight,based on the weight of component b); and component b-ii) is present inan amount of 10 to 80% by weight, based on the weight of component b).10. The process of claim 1 wherein component a-i) is present in anamount of 30 to 80% by weight, based on the weight of component a);component a-ii) is present in an amount of 20 to 70% by weight, based onthe weight of component a).
 11. The process of claim 2 wherein componenta-i) is present in an amount of 30 to 80% by weight, based on the weightof component a); component a-ii) is present in an amount of 20 to 70% byweight, based on the weight of component a).
 12. The process of claim 3wherein component a-i) is present in an amount of 30 to 80% by weight,based on the weight of component a); component a-ii) is present in anamount of 20 to 70% by weight, based on the weight of component a). 13.The process of claim 1 wherein component b-i) is present in an amount of30 to 80% by weight, based on the weight of component b); componentb-ii) is present in an amount of 20 to 70% by weight, based on theweight of component b).
 14. The process of claim 2 wherein componentb-i) is present in an amount of 30 to 80% by weight, based on the weightof component b); component b-ii) is present in an amount of 20 to 70% byweight, based on the weight of component b).
 15. The process of claim 3wherein component b-i) is present in an amount of 30 to 80% by weight,based on the weight of component b); component b-ii) is present in anamount of 20 to 70% by weight, based on the weight of component b). 16.The process of claim 1 wherein the polyether segments of component a-i)have a number average molecular weight of at least 6000 and thepolyether segments of component a-ii) have a number average molecularweight of 3000 to 12,000.
 17. The process of claim 2 wherein thepolyether segments of component a-i) have a number average molecularweight of at least 6000 and the polyether segments of component a-ii)have a number average molecular weight of 3000 to 12,000.
 18. Theprocess of claim 3 wherein the polyether segments of component a-i) havea number average molecular weight of at least 6000 and the polyethersegments of component a-ii) have a number average molecular weight of3000 to 12,000.
 19. The process of claim 4 wherein the polyethersegments of component a-i) have a number average molecular weight of atleast 6000 and the polyether segments of component a-ii) have a numberaverage molecular weight of 3000 to 12,000.
 20. The process of claim 10wherein the polyether segments of component a-i) have a number averagemolecular weight of at least 6000 and the polyether segments ofcomponent a-ii) have a number average molecular weight of 3000 to12,000.